The growth and diversity of RFID applications is progressing at an exponential rate and now includes NFC systems. The existing RFID system concepts, based on isolated reader and tag functionality, do not necessarily provide the optimum system level solution for an ever-increasing diversity of application areas. Many of these emerging application areas may require each element within the RFID or NFC system to possess dual mode reader/tag functionality or dual activity.
Several technical problems need to be addressed to realise a dual mode reader/tag functionality in which both reader and tag functionality exist within the same apparatus.
In known RFID architectures, reader and tag antenna functionalities are quite different. Dual mode reader/tag functionality could be achieved using two separate antennas, one for the reader functionality and one for the tag functionality within any system. However, close proximity of the antennas will result in interference between the antennas. This effect is especially acute for proximity or vicinity coupled systems where the coupling mechanism is magnetic. A solution to this problem would involve either positioning the antennas at mutual magnetic nulls, or including an enable/disable function so that each antenna would be disabled when not in use. The former would have the difficulty of the null being moved by external influence, the latter would never be completely disabled due to parasitism in components. These solutions also result in increased complexity, cost and size of the dual mode solution.
It would also be desirable to provide a dual mode reader/tag which can be implemented such that pre-existing readers do not need to be changed to ensure interoperability.